Fluoroelastomers classified as copolymers of vinylidene fluoride and hexafluoropropylene are relatively viscous in comparison to other elastomers. In order to process such elastomers on conventional equipment, such as mixers, calenders and extruders, it is known to incorporate various softeners and lubricants into the elastomer gum prior to processing and vulcanization.
The degree of effectiveness of conventional processing aids is considered as being proportional to the relative amount of the softener or lubricant that is incorporated into the fluoroelastomer. The use of high proportions of a processing aid, however, is not feasible because the aid remains in the elastomer and adversely affects the normally excellent properties of the final vulcanizate.
Various processing aids have been proposed, including a low molecular weight polyethylene. When used as a single additive, however, the polyethylene does not relieve the physical tension and nerve in fluoroelastomers.
Accordingly, the primary object of the present invention is to provide a fluoroelastomer processing aid composed of a plurality of components, which together provide a substantial improvement over conventional aids used in the same or comparable quantities. Another object is to provide such processing aid that will enhance, or will not significantly detract from, the properties of the vulcanizate.